Inactivation of friedel-crafts catalyst systems



United States Pate '1 INACTIVATION OF FRIEDEL-CRAFTS CATALYST SYSTEMSHelmuth G. Schneider, West'field, and Hans G. Goering, Elizabeth, N. J.,and Vincent F. Mistretta, Chicago, 11]., assignors to Esso Research andEngineering Company, a corporation of Delaware Application December 31,1953, Serial No. 401,576 2 Claims. (Cl. 260-943) This invention relatesto an improved method for deactivating catalyst residues and relatesmore particularly to the deactivation of residues of Friedel Craftscatalysts, such as aluminum chloride, used in the polymerization ofvarious types of unsaturated hydrocarbons.

Many types of hydrocarbon polymerizations employ metal halides of theFriedel Crafts type as catalysts. Among these polymerizations is thepolymerization of isoolefins, such as isobutylene, to solid rubberypolymers. Aluminum chloride is the most generally used of the FriedelCrafts catalysts, but aluminum bromide, titanium tetrachloride andzirconium tetrachloride are used also.

At the end of the reaction the product must be treated to completelydestroy residual catalyst and to prevent the product from going oficolor. It is known that a good proportion of the catalyst is actuallybound up with the polymer, i. e. it terminates the polymer chain. Ifthis catalyst is not released from the polymer and destroyed, theresultin product is so color unstable as to be unmarketable. Variousmaterials have been used for this purpose. For example, alcohols, suchas methanol and ethanol, and alltalis, such as sodium hydroxide, can beused. Sodium hydroxide is used because of its convenience, readyavailability, and cheapness. However, it has been considered necessaryto use a large excess of the caustic in order to completely eliminatethe catalyst. This in turn requires further washing to remove the excesscaustic from the polymer. This excessive washing results in theformation of emulsions which are difiicult to break. Furthermore, theuse of strong caustic causes the resulting polymer to lose colorstability.

In application Serial 316,556, filed October 23, 1952, and nowabandoned, in the name of Helmuth G. Schneider and William C. VanSiclen, it has been proposed to overcome these difficulties by adding atleast one volume of aqueous caustic containing to 100% molar excess ofsodium hydroxide to the reactor contents and allowing the mixture tostand at a temperature between and 65 C. for a time sufiicient tocomplete the reaction and cause the precipitation of the aluminatesalts, thus completely destroying the catalyst.

However, when it is desired to pass the reactor contents in heatexchange with the fresh feed to cool the feed, the precipitation ofsalts in such volume will plug up the exchanger tubes and cause the shutdown of the equipment for cleaning out. If the catalyst is notinactivated until after the heat exchange, the presence of catalyst inthe stream passing through the exchanger will cause additionalpolymerization resulting in deterioration of the product.

It is therefore the major object of the present invention to provide amethod for effectively inactivating (i. e., slowing the rate of thereaction to a low or negligible value) the catalyst used in thepolymerization of isoolefins While at the same time cooling the feed byheat exchange with the reactor efiiuent.

Patented Aug. 26, 1958 'In accordance with this invention, this andother obects are accomplished by carrying out the inactivation of thecatalyst in two stages. The reactor efiluent is contacted, as soon as itis withdrawn, with 0.23 to 1.2 weight percent of aqueous O to 1%caustic. This amount of caustic reduces the deterioration in molecularweight of the polymer by after polymerization sufliciently so that theeflluent can be passed in heat exchange with fresh feed. The polymereflluent from the heat exchanger is then treated to completely destroythe catalyst by adding 16 to 100% molar excess of caustic and settlingat 20 to 65 C. to precipitate all of the aluminum.

The invention is particularly adapted to processes for thepolymerization of solid polymers from isobutylene or a hydrocarbonfraction containing it by contacting the isobutylene, preferably in adiluent such as hexane, with finely divided solid aluminum chloride or aslurry thereof in hexane at a temperature between C. and +40 C. Thepolymer as it forms dissolves in the large excess of hexane present in.the reactor and is Withdrawn as a slurry with aluminum chloride.

The manner in which the present invention is carried out will be fullyunderstood from the following description when read with reference tothe accompanying drawing.

A mixture of hexane and pure isobutylene in line 1 is mixed withrecycled isobutylene and hexane in line 32. This recycled isobutylenehowever, contains a small amount of water as a contaminant. Theisobutylene is introduced by line 2 into distillation tower 3 Where theWater is removed overhead through line 4 with a small amount of thehydrocarbons. Pure, dry isobutylene-hexane mixture is withdrawn throughline 5 and passed through heat exchanger 6 and line 7 to cooler 8, whereit is cooled to the approximate polymerization temperature, e. g. 40 F.From cooler 8 it is passed by line 11 to the reactor 13. A slurry of 5%aluminum chloride in hexane at a temperature no higher than l0 F. isadded to reactor 13 by line 12. The catalyst slurry is added at a rateof 1 1b. AlCl per hour, per gallon feed and the slurry is mixed with thefeed by stirrer 14 so that the catalyst is maintained in suspension.Reactor 1? is a conventional low temperature reactor provided withexternal refrigeration by a conventional ethane cooler.

Polymer, as it is formed, dissolves in the large excess of hexanepresent in the reactor and is thus prevented from depositing on thesurfaces of the reaction vessel. The solution of polymer in hexane iswithdrawn as a slurry with aluminum chloride through line 15. Water ordilute caustic is added to the slurry in line 15 by means of line 45 andthe resulting mixture is passed through heat exchanger 6, where it coolsincoming feed. The heated polymer solution leaves the heat exchanger byline 16 and is contacted in orifice mixer 17 with the desired molarexcess of dilute caustic between 10 and 100% introduced through line 18to completely destroy the catalyst. This forms neutralization salts ofaluminum which are settled out in settler 1?, where two layers areformed, an upper layer consisting of a solution of polymer in hexane andisobutylene and a lower layer of dilute caustic containingneutralization salts of aluminum. The bottom layer is withdrawn throughline 2t) and the upper layer is passed by line 21 to flash drum 22,where the lower boiling materials are flashed oil through line 23. Apurge stream may be withdrawn through line 24, if desired. Apolyisobutylene hexane solution is withdrawn from the bottom of flashdrum 22 through line 25.

A solution of isobutylene polymer in hexane is withdrawn as a sidestream from flash drum 22 by line 26. A lubricating oil such as Essolube20 is added to this Perceht stream through line 27 as a heavycarrier'oil for the M01 pep g g 212 23 8 polymer. This mixture is passedto Still 28, where it iS Type quench cent on on weight weight distilledat a temperature of 200 F. under a pressure catalyst 1 332;; (stand) 5222; of 15 lbs. per sq.;in. gage. A stream containing approxicontrolmately 13% isobutylene and 85% hexane is withdrawn from the stillthrough line 29, combined with the overnone 17, 900 35 head from flashdrum 22 and passed into knockout drum gigg g- 291288 30, Where any waterpresent 1n this stream 1s settled out 1% aqueous NaOH- 24, 600 11 andremoved through line 31. The substantially dry mixcontrol Sample 27600ture of isobutylene and hexane is recycled to distillation d H I 1 hitower 3 by hne 32 F lme 2 i l nt di s r lleg wfi?quz cliti ii i fiiii ggeic s of n acetone-water Bottoms from st1ll 28 are passed by line 33 toa secsolution. 0nd still 34 oPerating at under a Prmsure of The abovedata show that as little as 0.23 wt. percent 15 lbs. per sq. 1n. gage.This stlll removes the last traces f Water or f 1% aqueous caustic hassome d i of 1sobutylene and the remainder of the hexane from ihg action,(the degree of deactivating being measured the solution of polymer H1011. The overhead withby the polymer molecular Weight drop from anaverage drawn by line 35 from the top of still 34- consists of aboutControl) While 12 Wt percent of aqueous caustic isobutylena, 35%116Xane, h Water from Steam is a good deactivating agent for solidaluminum chloride. 1 9 and Qthcr mmor C On3muents- Bottcms P The natureand objects of the present invention having Stlll 34 are Wllhdrilwll y11116 35 and Passed to a thud been thus described and illustrated, whatis claimed as Still 551137 is Operated at atmospheric Pressure and newand useful and is desired to be secured by Letters 300 F. to give anoverhead stream containing any dimer patent and trimer present. Drysteam is admitted through line 1 Process f preparing l i b l hi 38 thebase of Still 37 to facilitate Stripping Off the prises contacting amixture of isobutylene and hexane at light ends. Bottoms from still 37are passed by line 39 80 t0 +40 C i the presence f fi l id solid to airdfier 40 to rfimove any remaining moistm's- The Friedel Crafts catalystand contacting the reactor effluent dried -P y Solution is then nassed yline 41 to immediately with 0.23 to 1.2 wt. percent of water confilterpress 42 to remove any remaining aluminum salts. taming up to 1% causticto daactivate the catalyst, pass- The finished solution or" polyhutenein oil is then passed i the deactivated ffl t i h exchange with the byline 43 to storage tank fresh feed and washing the heat exchangedeffiuent with h followmg examples luusu'ate benfi3fit$ to be at leastequal volumes of aqueous caustic per volume of Obtamed by the Pracncc ofthe Present mventloni P reaction product, said caustic containingbetween 10 and Example 1 30 100 mol percent excess sodinm hydroxide overthat theo- A mixture of 30% isobutylene and 70% hexane was gi g gggs iiigg ifg zg ggg i g the can polymerized at C. in the presence of 0.95%finely tyst is aluminum chloride. divided aluminum chloride to yield asolution of 20% polyisobutylene in hexane slurried with 0.3 wt. percent40 References Cited in the fil f this patent aluminum chloride.Diflerent portions of the reactor efiluent were treated with ditferentamounts of water and dilute caustic and the degree of quenchingdetermined. The following data were obtained:

UNITED STATES PATENTS

1. PROCESS FOR PREPARING POLYISOBUTYLENE WHICH COMPRISES CONTACTING AMIXTUE OF ISOBUTYLENE AND HEXANE AT -80* TO +40*C. IN THE PRESENCE OFFINELY DIVIDED SOLID FRIEDEL CRAFTS CATALYST AND CONTACTING THE REACTOREFFLUENT IMMEDIATELY WITH 0.23 TO 1.2 WT. PERCENT OF WATER CONTAINING UPTO 1% CAUSTIC TO DEACTIVATE THE CATALYST, PASSING THE DEACTIVATEDEFFLUENT IN HEAT EXCHANGE WITH THE FRESH FEED AND WASHING THE HEATEXCHANGED EFFLUENT WITH AT LEAST EQUAL VOLUMES OF AQUEOUS CAUSTIC PERVOLUME OF REACTION PRODUCT, SAID CAUSTIC CONTAINING BETWEEN 10 AND 100MOL PERCENT EXCESS SODIUM HYDROZIDE OVER THAT THEORETICALLY NECESSARY TOREACT WITH THE CATALYST.